I need to change the rear seal on my T100 manual transmission. I got the seal, Napa brand, made in Japan by Koyo. I looked some info up on their products and found this page in their catalog interesting. Different nitriles listed, with temp ranges, and I learned silicone and gear oil don’t mix. At least their silicone doesn’t. Also it shows the wider range of silicone especially the high temp end. Only 10 deg more on the low end, -50 versus -40 for the best nitrile of the type they make. Silicone is 50-60 deg better on high temp. Hydrogenated Nitrile, NBR, goes to 140 versus silicone 170. It’s down on page 16-17, tried to copy and paste the page but couldn’t. Selection of seal 1.4. So I read oil seal catalogs like my grandpa, so what. 
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